III. Independent Work: d.I. Mendeleev

Exercise 1. Read the text.

Outstanding Russian Chemist d.I. Mendeleev

The second half of the 19^lh century was a period of rapid growth of chemistry. Among those who contributed to its further development was Dmitriy Mendeleev, the discoverer of the Periodic Law of the Elements.

Today the Periodic Law is studied by millions of secondary school children and by students at higher education establishments of natural sciences and engineering. It is studied by philosophers, historians and teachers. The Law serves as a basis for thousands of researches. The Periodic Law crossed national boundaries and has become the property of all nations, just like the works of Newton, Copernicus, Lomonosov, Darwin, Pavlov, Lobachevsky and Einstein.

Dmitry Mendeleev expressed the essence of his Law as follows: "The properties of the elements and, consequently, the properties of the simple and complex bodies formed by them are periodic functions of their atomic weights". When atomic weight increases, the chemical elements periodically and at certain intervals show similar properties. After deep analysis of literature and experimental data on the properties of elements, Mendeleev arranged all the elements in a table consisting of vertical groups and horizontal periods. In this table all the data on the properties of the elements and their compounds are collected and arranged into a system.

Before Mendeleev, several chemists tried to systematize the elements. Among them were German, English and French scientists. But they couldn't do that.

It was only after gallium, scandium and germanium were discovered in France, Sweden and Germany and after the properties of a number of elements predicted by Mendeleev were confirmed, and finally after a debate lasting for several years in journals that Mendeleev was recognized as the author of the Periodic Law.

In a few years Mendeleev was elected an honorary member of the American, English, Rome, Berlin, Belgian, Danish, Cracow and other Academies of Sciences; a member of the Royal Societies of London and Edinburgh and an honorary doctor of Cambridge, Oxford and other universities. Altogether 150 scientific and educational institutions in various countries elected him an honorary member. The Academy of Sciences and the Mendeleev Society award the Mendeleev Prize and the Mendeleev Gold Medal for outstanding research work in chemistry.

Exercise 2. Make up a vocabulary of new words, write them down in your vocabularies.

Exercise 3. Make up a plan of the text.

Exercise 4. What is the main idea of the Periodic Law of the Elements? Exercise 5. Tell your group about Dmitriy Mendeleev.

LESSON THIRTY-FOUR

I	Speaking	Chemical Elements. Properties of Substances
II	Grammar	1. Дієслова у Past Perfect Continuous (§90). 2. Складний додаток після дієслів to want, to expect. Виразshould/would like to (§91)
III	Independent Work	Chemical Elements of Living Matter